2019-10-01 08:13:41

by Icenowy Zheng

Subject: [PATCH 2/3] drm/sun4i: dsi: fix DRQ calculation

According to the BSP source code, when calculating the magic DRQ value
outside burst mode, a formula of "lcd_ht - lcd_x - lcd_hbp", which is
interpreted as right margin (HFP value). However, currently the
sun6i_mipi_dsi driver code calculates it wrongly as HFP + sync length,
which lead to timing error.

Fix the DRQ calculation by change it to use HFP.

Signed-off-by: Icenowy Zheng <[email protected]>
---
drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index c86e11631ebc..2d3e822a7739 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -436,9 +436,9 @@ static void sun6i_dsi_setup_burst(struct sun6i_dsi *dsi,
SUN6I_DSI_BURST_LINE_SYNC_POINT(SUN6I_DSI_SYNC_POINT));

val = SUN6I_DSI_TCON_DRQ_ENABLE_MODE;
- } else if ((mode->hsync_end - mode->hdisplay) > 20) {
+ } else if ((mode->hsync_start - mode->hdisplay) > 20) {
/* Maaaaaagic */
- u16 drq = (mode->hsync_end - mode->hdisplay) - 20;
+ u16 drq = (mode->hsync_start - mode->hdisplay) - 20;

drq *= mipi_dsi_pixel_format_to_bpp(device->format);
drq /= 32;
--
2.21.0

2019-10-03 05:08:30

by Jagan Teki

Subject: Re: [linux-sunxi] [PATCH 2/3] drm/sun4i: dsi: fix DRQ calculation

Hi,

On Tue, Oct 1, 2019 at 1:34 PM Icenowy Zheng <[email protected]> wrote:
>
> According to the BSP source code, when calculating the magic DRQ value
> outside burst mode, a formula of "lcd_ht - lcd_x - lcd_hbp", which is
> interpreted as right margin (HFP value). However, currently the
> sun6i_mipi_dsi driver code calculates it wrongly as HFP + sync length,
> which lead to timing error.
>
> Fix the DRQ calculation by change it to use HFP.
>
> Signed-off-by: Icenowy Zheng <[email protected]>
> ---
> drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> index c86e11631ebc..2d3e822a7739 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> @@ -436,9 +436,9 @@ static void sun6i_dsi_setup_burst(struct sun6i_dsi *dsi,
> SUN6I_DSI_BURST_LINE_SYNC_POINT(SUN6I_DSI_SYNC_POINT));
>
> val = SUN6I_DSI_TCON_DRQ_ENABLE_MODE;
> - } else if ((mode->hsync_end - mode->hdisplay) > 20) {
> + } else if ((mode->hsync_start - mode->hdisplay) > 20) {
> /* Maaaaaagic */
> - u16 drq = (mode->hsync_end - mode->hdisplay) - 20;
> + u16 drq = (mode->hsync_start - mode->hdisplay) - 20;

I have similar patch in the ML, which required commit details
commented by Chen-Yu [1]. So, I'm trying to send it accordingly, let
me know if you have issues.

[1] https://patchwork.freedesktop.org/patch/305920/